Evidence for raw acoustics as the target of phonetic imitation

Abstract

Phonetic imitation (also called convergence or accommodation) occurs when talkers alter their production towards speech they hear, even in lab settings without explicit instruction to imitate. Though general evidence for imitation is robust, much of the existing work does not distinguish between convergence towards a linguistic target versus convergence towards an acoustic target. This study presents a direct test case of these hypotheses through spontaneous imitation of the English alveolar sibilant /s/ in a delayed shadowing task. Participants first produced /s/-initial words, then were exposed to model speech with either enhanced or reduced spectral mean (SM) on /s/, and finally produced /s/-initial words again post-exposure. The model talker had higher than average baseline SM, so raw acoustic values were higher than those of most participants. All participants exposed to the enhanced stimuli raised SM, converging towards both the raw acoustics of the model talker and the linguistic pattern of enhancement. However, participants exposed to the reduced stimuli also raised SM. This diverged from the linguistic pattern of reduction but converged towards the raw acoustics of the model talker, whose SM was still higher than participants' even when reduced. These results suggest raw acoustics can be the target of phonetic imitation. Possible interactions with phonological contrast, implications for the perception-production link, and methodological considerations for future imitation studies are discussed.